Two-cycle internal combustion engine

ABSTRACT

A two-cycle internal combustion engine having an electric ignition system and characterized in that a suitably shaped recess is disposed inside the cylinder head, thereby forming a combustion chamber. A device for controlling the quantity of fuel supply and a device for controlling the flow of exhaust gas are operated relatively to each other in such a way that the flow of exhaust gas is increased or decreased in response to increase or decrease in the supply of fuel.

U Umted States Patent 1191 1111 3,817,227 Onishi June 18, 1974 [54]TWO-CYCLE INTERNAL COMBUSTION 3,400,702 9/1968 Watkins 123/65 R ENGINEFOREIGN PATENTS OR APPLICATIONS Inventor: ig i i, 1-1 17,176 5/1956Germany 123/73 R Higashiyama, 3-chome, Kanazawa, 572,529 2/1924 France123/73 V Japan 865,233 5/1952 Germany 123/73 A 605,610 7/1948 GreatBritain 123/65 R Flledi 1972 67,520 7 10/1957 France 123/65 WA [21]Appl. No.: 232,325

Primary Examiner-Charles .1. Mlyhre Assistant Examiner-W. Rutledge, Jr.[30] Forelgn Apphcauon Pnomy Data Attorney, Agent, or FirmBlum MoscovitzFriedman Feb. 25, 1971 Japan ..46-9703 & Kaplan [52] US. Cl. 123/73 A,123/65 WA, [57] ABSTRACT 51 1111.01. F02b 25/20, F02d 9/04, F02d 9/10 A9'. cmbusfion l having [58] Field of Search 1213/65 R 65 w 65 W Aelectric ignltlon system and characterized in that a 123 73 R 73 98suitably shaped recess is disposed inside the cylinder head, therebyforming a combustion chamber. A de- [56] References Cited vice forcontrolling the quantity of fuel supply and a device for controlling theflow of exhaust gas are oper UNITED STATES PATENTS ated relatively toeach other in such a way that the 13 5 lsmdefson flow of exhaust gas isincreased or decreased in repencer 2 L 5/1936 Harper-m. sponse toIncrease or decrease In the supply of fuel 2,064,983 12/1936 Lesage123/65 A 7 Claims, 7 Drawing; Figures PATENTEDJUH 18 I974 sum 2 or 3Full Open Exhduat V 1 Contr l VUIVQ Closb v v Full Op'on TWO-CYCLEINTERNAL COMBUSTION ENGINE BACKGROUND OF THE INVENTION This inventionrelates to two-cycle, piston-typeinternal combustion engines in whichthe gas mixture provided by carburetor system or injector system iscompressed inside the cylinder, and more particularly to a two-cycleinternal combustion engine employing a loop or cross-scavenging system.

The conventional two-cycle internal combustion engine of loop orcross-scavenging type, particularly of crank case compression type isstructurally simple and can be manufactured at a low cost. On the otherhand, however, it has several drawbacks. For example, misfire oftentakes place even if an easily combustible mixture with a high fuel-airratio is used in the no-load or part-load operating condition. Thisresults in an irregular combustion state involving unpleasant exhaustsounds and rough vibration. Furthermore the specific fuel consumption israised and the noxious component in the exhaust gas is increased.Generally, in order to increase the charging efficiency in the priorart, the exhaust pipeline is designed to be suitable as to size andshape so that the negative pressure wave produced in the pipe due to theflow of exhaust gas is reversely introduced into the cylinder. Thisarrangement is effective during high load operation, while it serves asa significant factor causing misfire, because, at a light load where asmall amount of gas mixture is applied, the supplied gas mixture isunnecessarily mixed with the residual gas.

SUMMARY OF THE INVENTION In view of the foregoing, the present inventionhas, as its principal aim, the provision of an improved twocycleinternal combustion engine operable at a high combustion efficiency ineach cycle even at a relatively low fuel-air ratio, and capable ofpreventing misfire irrespective of operating condition, minimizingvibration and noise of engine, decreasing the specific fuel consumption,i.e., increasing the thermal efficiency, and purifying the exhaust gas.

With this aim in view, an object of this invention is to provide atwo-cycle internal combustion engine in which a suitably shaped recessis disposed inside the cylinder head, thereby forming a combustionchamber, an exhaust gas control part disposed in the exhaust pipelineand a fuel supply control part are relatively operated in such a waythat at a part-load operation the gas mixture flow into the cylinder isreasonably slowed and stratified and the mixture is securely sent insaid recess space whereby stable combustion is maintained in each cycleeven at a low fuel-air ratio, misfire is prevented, and the exhaust gasis purified.

Another object of this invention is to provide a twocycle internalcombustion engine in which the squish effect is brought about in thevicinity of the top dead center whereby a higher ignitability ismaintained and combustion is accelerated.

Still another object of this invention is to provide a twofcycleinternal combustion engine in which an ingition plug is disposed in aspecific position and said recess part whereby a higher ignitability isachieved.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings illustrate an embodimentof the present invention wherein:

FIG. I is a schematic sectional side view showing the overallconstruction;

FIG. 2 is an enlarged view of the cylinder portion, showing the state ofdistribution of the fuel particles in the injected mixture gas;

FIG. 3 is a schematic sectional view taken along line 1-1 of FIG. 2 inthe direction of the arrows;

FIGS. 4 and 5 are schematic sectional views taken along lines 2-2 and3-3, respectively, of FIG. 3, in the direction of the arrows and showingthe state of squish flow;

FIG. 6 is a graphic representation showing the relationship between theexhaust control valve and the throttle valve with respect to valveopening; and

FIG. 7 is a diagrammatic representation of a valvecontrolling linkage.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, there isschematically illustrated a Schnuerle scavenging type two-cycle internalcom bustion engine having a crank case compression systern, wherein ascavenging port 3 and an exhaust port 4 are opened/closed by the motionof a piston 2 reciprocatively disposed in a cylinder 1.. An exhaustcontrol valve 6 is provided in an exhaust pipe 5 connected to exhaustport 4. This exhaust control valve is located at a small distance fromsaid exhaust port 4 whereby a prechamber 20 is formed.

A carbureter 26 is disposed in an intake pipe 7 communicating with acrank case 12. A control lever 9 of a throttle valve 8 of a fuel-supplycontrol means which is to control the fuel supply and a control lever 10of exhaust control valve 6 of an exhaust-gas control means areinterlocked by way of a link mechanism 11, as shown schematically inFIG. 1. Thus, when the throttle valve 8 is moved in an openingdirection, namely in the direction of increasing fuel supply, theexhaust control valve 6 is moved also in an opening direction, so thatthe exhaust outflow resistance is reduced.

A one-way, flexible, springer leaf valve (not shown) which serves tostop the back flow from the crank case 12 is provided in a part 19 wheresaid intake pipe is connected to the crank case 12. The gas mixturecompressed in the crank case 12 by the motion of piston 2 is supplied tothe cylinder 1 from the scavenging port 3 by way of scavenging passages13, which are located opposite to each other on the both sides of thecylinder respectively.

The inside of a cylinder head 14 is shaped as shown in FIGS. 2 and 3which show a recess 15 formed in the neighborhood of the center of thecylinder head. More specifically, the recess is formed to becomegradually deeper in the direction of the gas flow in the cylinder, inwhich the gas stream turns from the upward to downward direction in thevicinity of the cylinder head. The deepest part of the recess 15 islocated on the front side of the direction along which the streamadvances, and the space of the recess is wide enough so that the streamturning round in the axial direction of the cylinder makes a swirlingmotion. The: inside of the recess has no part wider than its open end sothat the shape of the recess does not become constricted at its openend.

The inner surface 17 of the cylinder head 14 around the recess 15 isshaped corresponding to the top surface' 18 of the piston, and the gasesheld between the surface 17 and the top of the cylinder head produce asquish stream near the top dead center. This squish stream can bestrengthened or weakened by changing the relative relationship betweenthe surface 17 and the top surface 18. Namely, the strength of thesquish stream can be determined by the distance between surfaces 17 and18 at the point of the top dead center, the shapes of surfaces 17 and18, etc.

This engine of the invention is operated in the following manner:

The gas mixture sucked into the crank case 12 by the motion of thepiston 2 by way of the throttle valve 8 of carbureter 26 and the intakepipe 7 is compressed and pressurized by the down motion of the piston 2.The pressurized gas burnt in the cylinder is expanded by the down motionof the piston. When the exhaust port 4 is opened, the exhaust gas isemitted into prechamber 20 and then is exhausted to the exterior fromthe exhaust port via the exhaust control valve 6.

During light load operation where the intake air is throttled by thethrottle valve 8, the exhaust control valve 6 also is throttled by theinterlocking link mechanism l1, and valve 6 becomes nearly closed. As aresult, the exhaust gas is subjected to resistance at the valve 6, andthe pressure in the prechamber 20 is increased. Therefore, the pressurein the cylinder 1 is not rapidly lowered, and flowing of the scavenged(or supplied) gas into the chamber 1 by the opening of the scavengingport 3 is slowed. In other words, the subsequently supplied gas mixtureis mixed and diffused into the residual exhaust gas only to a smallextent. Thus, the gas mixture is fed into the recess of the cylinderhead without sacrificing the combustibility even if the air-fuel ratiois determined to be larger than the stoichiometric value. In otherwords, the supplied gas is stratified in the form of an are or sphere inthe cylinder as indicated by the dot group in FIG. 2 before the gas isappreciably mixed with the residual burnt gas, and there is formed apattern of stream of the supplied gas flowing moderately into the recess15. The purpose of the exhaust valve 6 in its nearly closed position isto reflect the interfering wave reversely propagated from the exhaustpassage 5 (positioned after the valve 6) into the cylinder 1, keep thestream in the cylinder 1 from being disturbed, and minimize thedisturbing influence which may be introduced into the cylinder from theexhaust pipeline. This function contributes largely to perfecting saidstratified gas supply.

It has been experimentally found that it becomes difficult to maintainstable part-load operation when the volume of the prechamber is toosmall. This is because the pressure drop in the cylinder 1 is slowed,the exhaust gas flows back through the gas supply passage 13 to reach asfar as the crank case 12 when the scavenging port 3 is opened, and thecylinder is charged with the gas containing a large amount of exhaustgas in the subsequent cycle of ignition, to result in misfire. If theopening of the exhaust control valve 6 is increased in order to solvethe above trouble, this means that the control valve 6 is substantiallyremoved.

While, if the exhaust control valve 6 is positioned too distant from theexhaust port 4, the volume of the prechamber 20 becomes too large, thepressure drop in the cylinder 1 goes as in the case where the valve 6 isnot provided, and the pressure wave by the injected gas is sent back asa reflection wave of positive pressure to the cylinder l at certain timeintervals, to disturb the stratified gas. In this instance also, theexhaust control valve has no significance. It has been experimentallyascertained that desirable combustion causing no misfire and allowingleast bypassed fuel can be obtained when the volume of the prechamber 20is between l/lO and 3/l0 that of the engine stroke. As for combustion,it was also found that there is relationship between the throttle valve8 and the exhaust control valve 6 with respect to opening. For example,the mean effective pressure is gradually reduced under the conditionthat the throttle valve 'is kept opened at a certain opening, theinterlocking link 11 is released, and only the opening of the exhaustcontrol valve 6 is gradually reduced from its full opening. A similarresult can be obtained under the condition that the exhaust controlvalve is kept opened at a certain opening, and the throttle valve isclosed from its full opening.

For combustion where the specific fuel consumption is reduced withoutcausing misfire, it is desirable to maintain the following relationshipbetween the two valves with respect to valve opening. According toexperiments, this relationship is as shown by the curve in FIG. 6 inwhich the opening of the exhaust control valve 6 is very small in therange of small opening of the throttle valve 8, and the exhaust controlvalve 6 rapidly reaches its full opening position when the opening ofthe throttle valve 8 is above a certain value.

Referring to FIG. 7, it will be seen that between the levers 9 and 10there is a cam 11a having a camming edge 11b and supported for freeswinging movement about a pivot pin 11b. An elongated link is pivotallyconnected at its opposite ends to the lever 9 and the cam 11a. The lever10 is urged in a counter clockwise direction, as viewed in FIG. 7,toward the cam 110 by a spring 10b, and the lever 10 carries acamfollower roller 10a engaging the camming edge 11b. This is oneexample of a possible embodiment of the linkage 11 for interconnectingthe levers 9 and 10 so as to control the movement of the valves 8 and 6,respectively. The lever 9 can be swung in the opening and closingdirections as indicated by the double-headed arrow, and the lever 10will be correspondingly swung in opening and closing directions throughthe linkage means 11 of FIG. 7. Because of the shape of the camming edge11b the extent of opening and closing of the valve 6 by turning of thelever 10 will have with respect to the opening and closing of the valve8 by the lever 9 the relationship shown in FIG. 6.

The gas supplied to the cylinder 1 relatively slowly and in thestratified form is introduced to the recess 15 of the cylinder headround about the central zone 22 in the cylinder 1. The stream of thisgas is in spherical form and subjected to a centrifugal force and,hence,

' the supplied gas mixture whose specific gravity is larger than that ofthe residual gas is positioned on the outer side. The fuel particlescontained in the gas mixture have a large apparent specific gravity.Consequently the fuel particles are located further at the outer side,and the fuel-air ratio distribution becomes higher toward the outermostzone of the supplied mixture gas. This state is schematically shown bythe density distribution of dots representing mixture gas supply in FIG.2.

The recess is shaped to become gradually deeper so that the supplied gasflows therein smoothly. The recess is deepest on the side of the frontof the gas stream. in this deepest portion the supplied gas is securelyre ceived and temporarily held. A spark plug 16 is mounted in a deeppart 21 so that the spark plug is positioned in a quiet atmosphereinside the recess and is beyond the gas stream in the cylinder. Thisfacilitates ignition and spread of the initial flame.

According to this embodiment, a squish stream is produced near the topdead center due to the top 18 of the piston and the inner surface 17 ofthe cylinder head. Practically, for example, as shown in FIGS. 3, 4 and5, the squish stream 23 due to the top surface of the shallow portion ofthe recess 15 and the top of the piston serves to drive the suppliedmixture into the deep part of the recess. The squish stream 25 oppositeto the squish stream 23 acts to keep the supplied gas mixture fromflowing out of the recess. The function of the squish streams from theboth sides of the recess is to press and spread the supplied gas mixtureover the wall of the recess. As a result, the gas mixture is thicklystagnated in the vicinity of the corners 27 of the recess FIG. 5, ratherthan in the central portion of the recess. lf, therefore, the spark plugis positioned eccentrically from the center recess line (FIG. 3), morestable ignition can be realized. It has been experimentally ascertainedthat the above arrangement is effective for stable ignition even whenthere remains in the recess a swirling stream having a rotating vectorin the axial direction of the cylinder.

As has been described above, the engine of this invention can be drivenwith a thin gas mixture whose airfuel ratio is, for example, 15 to 18,by suitably determining the correlation between the exhaust controlvalve 6 and the shape of the recess 15 of the cylinder head. Especiallyunder part-load and no-load operating conditions, misfire and irregularcycle are minimized or eliminated. This makes it possible to reduce thenumber of rotations set for idling and to minize the fuel consumptionduring idling rotation.

According to the invention, stable combustion is maintained at a largeair-fuel ratio. This in turn increases the efficiency of purifying theexhaust gas. The concentration of carbon monoxide (CO) is reduced below1/10 compared with that in the prior art. The component of unburnthydrocarbon is also reduced to about half that in the prior art by theuse of exhaust control valve 6, thereby preventing ineffectivedispersion of fuel gas due to stratification and thus minimizing bypassgas flow out to the exterior. inherently, in the two-cycle engine, thereremains a large amount of residual gas component which, however, servesas an inactive gas. This is why only very little nitrogen oxide (NOx)component is produced.

The combustibility at a large air-fuel ratio and the minimized fuelbypass escape contribute to improvement on the specific fuelconsumption, i.e., on the thermal efficiency. Thus, stable combustionhaving a small cycle variation is realized and the engine vibration andnoise are reduced.

According to the invention, the peak value of the exhaust jet velocityduring idling and part-load operation is suppressed and smoothed byvirtue of the exhaust control valve and, hence, the exhaust sound fromthe end of the exhaust pipe is reduced to permit quiet engine drive.

In the foregoing embodiment, an engine using a carbureter has beendescribed. As the fuel supply means, a suitable injection system may beemployed instead of carbureter. For example, an intake pipe injection,crank case injection, injection into the cylinder from the scavengingport, injection into the cylinder from the cylinder or from the cylinderhead, etc. may be used. The invention permits use of various fuels, forexample, gaseous fuel such as LPG, and low quality fuel such as keroseneoil.

According to the invention, the device for controlling the amount offuel injection into the cylinder, and the device for controlling theflow of the exhaust gas (such as the exhaust control valve) arerelatively operated whereby the flow of the exhaust gas is decreased orincreased in response to decrease or increase in the fuel supply. Thisconcept can be applied to Diesel compression ignition engines. ln thiscase, during no loador part-load operation where a small amount of fuelis injected therein, it is necessary to throttle the exhaust controlvalve so that a suitable amount of air corresponding to the existingload is supplied to the combustion chamber in the stratified form. Bythis arrangement, it becomes possible not only to reduce the pump lossfor air supply but also to hold a relatively large amount of residualgas. As a result, the compression initial temperature, i.e., thecompression end temperature, can be raised, thus making available asufficient temperature rise necessary for the engine operable at a lowcompression ratio, and the fuel ignition delay time can be reduced.Namely, it has been experimentally conformed that the Diesel knockingphenomenon can be almost perfectly eliminated. Because the combustioncan be maintained at a low compression ratio and there remains inactiveresidual gas, the component of nitrogen oxide (NOx) which is a typicalproblem of Diesel engines can be largely reduced to about 200 ppm at thefull load. it is apparent that the invention, when applied to Dieselengines, is particularly useful and practical.

What ss aitnss js 1. in a two-cycle internal combustion engine having anelectrical ignition system, elongated cylinder means having a cylinderaxis and formed in its interior at one end region with a combustionrecess which becomes gradually deeper in the direction of gas flow inthe cylinder up to a deepest portion of said recess situated at thatside of said axis toward which the gas stream flows after crossing saidaxis, the direction of gas flow changing beyond said deepest portion ofsaid recess and said recess having its maximum cross sectionin a planenormal to said axis at that part of said recess which is most distantfrom the deepest portion of said recess, so that said recess is notconstricted at its entrance end, exhaust port means and scavenging portmeans communieating with said cylinder means, piston means reciprocatingin said cylinder means for opening and closing said exhaust port meansand said scavenging port means, a crank case situated beneath saidcylinder means and receiving fuel to be compressed by said piston meanswhile the latter moves away from said recess before the gas stream flowsinto said cylinder means through said scavenging port means, supply portmeans communicating with said crank case for supplying fuel thereto,angularly adjustable supply valve means and angularly adjustable exhaustvalve means respectively located in said supply port means and saidexhaust port means for controlling the flow of gases therethrough, andlinkage means operatively connected with said supply valve means andsaid exhaust valve means for automatically opening and closing saidexhaust valve means during opening and closing of said supply valvemeans, respectively, said linkage means transmitting movement from saidsupply valve means to said exhaust valve means and providing for everyangular position of said supply valve means a predetermined angularposition for said exhaust valve means, said linkage means including apair of levers respectively connected with said angularly adjustablesupply valve means and said angularly adjustable exhaust valve means forrespectively swinging both of the latter valve means, a swingable camsituated between said levers, a link extending between the leverconnected to said supply valve means and said cam for swinging said camin response to angular movement of said supply valve means, a camfollower fixedly carried by said lever which is connected to saidangularly adjustable exhaust valve means, said follower engaging acamming surface of said cam, the latter camming surface having aconfiguration which provides a predetermined angular position of saidexhaust valve means for every angular position of said supply valvemeans, and a spring operatively connected with said lever connected tosaid exhaust valve means for maintaining said follower in engagementwith said camming surface.

2. The combination of claim 1 and wherein said cylinder means has a pairof opposed oppositely inclined surface portions defining part of saidcombustion recess for producing a squish effect.

3. The combination of claim 1 and wherein a spark plug of saidelectrical ignition system is situated at said deepest portion of saidrecess and communicates through said deepest portion of said recess withthe interior of said cylinder means.

4. The combination of claim 3 and wherein said spark plug iseccentrically positioned beyond said axis.

5. The combination of claim 1 and wherein said exhaust port meansdefines upstream of said exhaust valve means a prechamber for receivinggas in said exhaust port means prior to flow of gas past said exhaustvalve means.

6. The combination of claim 5 and wherein said prechamber has a volumewhich is between 1/10 and 3/10 the volume of the stroke of said pistonmeans.

7. In a two-cycle internal combustion engine, fuelsupply control meansfor controlling the fuel supply and exhaust-gas control means forcontrolling the flow of exhaust gas, and means interconnecting both ofsaid control means for incrasing and decreasing the amount of exhaustgas flow in response to an increase or decrease, respectively, in thefuel supply, whereby combustion is maintained at a relatively lowcompression ratio, each of said control means including a duct and atiltable valve therein, and said means interconnecting both of saidcontrol means including a mechanical transmission means extendingbetween and operatively connected to said tiltable valves for providingfor each angular position of said tiltable valve for said fuelsupplycontrol means a predetermined angular position for said tiltable valveof said exhaust-gas control means, said mechanical transmission meansincluding a pair of levers respectively connected with said tiltablevalves for respectively swinging the latter when said levers turn, a camswingably mounted between said levers, a link interconnecting the leverwhich is connected to said tiltable valve of said fuel-supply controlmeans with said cam, a cam follower fixedly carried by the other of saidlevers and engaging a camming surface of said cam which has aconfiguration providing for the tiltable valve of said exhaustgascontrol means said predetermined angular position for each angularposition of said tiltable valve of said fuel-supply control means, and aspring operatively connected with the latter lever for maintaining saidcam follower in engagement with said camming surface.

1. In a two-cycle internal combustion engine having an electricalignition system, elongated cylinder means having a cylinder axis andformed in its interior at one end region with a combustion recess whichbecomes gradually deeper in the direction of gas flow in the cylinder upto a deepest portion of said recess situated at that side of said axistoward which the gas stream flows after crossing said axis, thedirection of gas flow changing beyond said deepest portion of saidrecess and said recess having its maximum cross section in a planenormal to said axis at that part of said recess which is most distantfrom the deepest portion of said recess, so that said recess is notconstricted at its entrance end, exhaust port means and scavenging portmeans communicating with said cylinder means, piston means reciprocatingin said cylinder means for opening and closing said exhaust port meansand said scavenging port means, a crank case situated beneath saidcylinder means and receiving fuel to be compressed by said piston meanswhile the latter moves away from said recess before the gas stream flowsinto said cylinder means through said scavenging port means, supply portmeans communicating with said crank case for supplying fuel thereto,angularly adjustable supply valve means and angularly adjustable exhaustvalve means respectively located in said supply port means and saidexhaust port means for controlling the flow of gases therethrough, andlinkage means operatively connected with said supply valve means andsaid exhaust valve means for automatically opening and closing saidexhaust valve means during opening and closing of said supply valvemeans, respectively, said linkage means transmitting movement from saidsupply valve means to said exhaust valve means and providing for everyangular position of said supply valve means a predetermined angularposition for said exhaust valve means, said linkage means including apair of levers respectively connected with said angularly adjustablesupply valve means and said angularly adjustable exhaust valve means forrespectively swinging both of the latter valve means, a swingable camsituated between said levers, a link extending between the leverconnected to said supply valve means and said cam for swinging said camin response to angular movement of said supply valve means, a camfollower fixedly carried by said lever which is connected to saidangularly adjustable exhaust valve means, said follower engaging acamming surface of said cam, the latter camming surface having aconfiguration which provides a predetermined angular position of saidexhaust valve means for every angular position of said supply valvemeans, and a spring operatively connected with said lever connected tosaid exhaust valve means for maintaining said follower in engagementwith said camming surface.
 2. The combination of claim 1 and whereinsaid cylinder means has a pair of opposed oppositely inclined surfaceportions defining part of said combustion recess for producing a squisheffect.
 3. The combination of claim 1 and wherein a spark plug of saidelectrical ignition system is situated at said deepest portion of saidrecess and communicates through said deepest portion of said recess withthe interior of said cylinder means.
 4. The combination of claim 3 andwherein said spark plug is eccentrically positioned beyond said axis. 5.The combination of claim 1 and wherein said exhaust port means definesupstream of said exhaust valve means a prechamber for receiving gas insaid exhaust port means prior to flow of gas past said exhaust valvemeans.
 6. The combination of Claim 5 and wherein said prechamber has avolume which is between 1/10 and 3/10 the volume of the stroke of saidpiston means.
 7. In a two-cycle internal combustion engine, fuel-supplycontrol means for controlling the fuel supply and exhaust-gas controlmeans for controlling the flow of exhaust gas, and means interconnectingboth of said control means for incrasing and decreasing the amount ofexhaust gas flow in response to an increase or decrease, respectively,in the fuel supply, whereby combustion is maintained at a relatively lowcompression ratio, each of said control means including a duct and atiltable valve therein, and said means interconnecting both of saidcontrol means including a mechanical transmission means extendingbetween and operatively connected to said tiltable valves for providingfor each angular position of said tiltable valve for said fuel-supplycontrol means a predetermined angular position for said tiltable valveof said exhaust-gas control means, said mechanical transmission meansincluding a pair of levers respectively connected with said tiltablevalves for respectively swinging the latter when said levers turn, a camswingably mounted between said levers, a link interconnecting the leverwhich is connected to said tiltable valve of said fuel-supply controlmeans with said cam, a cam follower fixedly carried by the other of saidlevers and engaging a camming surface of said cam which has aconfiguration providing for the tiltable valve of said exhaustgascontrol means said predetermined angular position for each angularposition of said tiltable valve of said fuel-supply control means, and aspring operatively connected with the latter lever for maintaining saidcam follower in engagement with said camming surface.